The Argus Sour Crude Index is a crude oil index published by Argus media. It is calculated by combining prices from three blends of oil from the Gulf of Mexico: each blend consists of oil from several fields.
It became a major benchmark when it was adopted (in 2009) by the Saudi national oil company, Aramco, as the benchmark for pricing exports to the US, as the price is less volatile than that of the previous benchmark used for the purpose, West Texas Intermediate.
As the name implies it is a high sulphur “sour” crude oil. It has an API gravity of approximately 29, heavier than WTI.
Argus Sour Crude Index futures are traded on the CME Group's NYMEX exchange.